1. Field of the Invention
This invention relates to a block-graft copolymer useful as a material for various functional membranes including an oxygen enrichment membrane.
2. Description of the Prior Art
At present, many attempts are made on the development of function polymer materials used for various purposes.
Dimethylpolysiloxane is known as a material for high enrichment of oxygen, but, when used in the form of a thin membrane, it can not stand use because of its weak cohesion. For this reason, it is attempted to form the material as a block copolymer to remedy its disadvantage. However, the block copolymer, although useful for increasing mechanical strength, can only afford to expect the oxygen enrichment and permeability corresponding only to the proportion held by dimethyl polysiloxane, raising a problem that the oxygen enrichment performance decreases in proportion thereto.
Polyethylene oxide, polyethylene-imine and the like are capable of forming a complex with a salt of metals such as lithium, sodium and uranium, and attempts have been made on how to practically separate these metal salts. However, no practical means for the separation is available at present.
Dimethylpolysiloxane, polyethylene oxide and polymers having an amino group or carboxyl group have biocompatibility, and some of them are used as biomedical materials such as antithrombrogenic materials, bioseparator materials and cell culturing materials. In particular, recently noted are polymeric materials, particularly block copolymers, containing the above dimethylpolysiloxane or polyethylene oxide as a component, which is a multiphase polymer with clear micro domain structure. However, in order to obtain the block copolymer finely divided into multiphases, no other way is available than producing it according to a living anionic polymerization method, and yet this method may restrict the manner of combination of monomers. Moreover, since the domain size of microphase-separated gyration is governed by the radius of inertia, there is a problem that the domain size in the block copolymer can be controlled only with difficulty.
Polyoxyethylene oxide and so forth have attracted notices as solid electrolytes since they are capable of forming a complex with an alkali metal salt as mentioned above. However, the polyethylene oxide, for example, starts to crystalize even in the form of a complex when it has a polymerization degree of 20 or more, to lower the performance as a solid electrolyte. Accordingly, there is a problem that the performance as a solid electrolyte can not be enhanced by making the molecular weight larger.